The present invention relates to an apparatus and method for heat-setting yarn. More particularly, the present invention is an apparatus and method for heat-setting bulk continuous filament (BCF) yarns with hot atmospheric air.
Background art methods for making BCF yarns for carpets typically include the steps of twisting, heat-setting, tufting, dyeing and finishing. In particular, heat-setting of twisted yarn is an important step in converting BCF yarns to carpets. Heat-setting develops crimp and locks the twist memory in the BCF yarns. The development of crimp and twist memory have a significant impact on yarn bulk and newness retention of finished carpets.
Two types of heating-setting methods are used in continuous heat-setting machines of the background art. The first type uses pressurized steam (i.e., saturated or near saturated steam). The most common pressurized steam heat-setting machine in the background art is referred to as a Superba® machine and is made by Superba of Mulhouse, France or American Superba, Inc. of Charlotte, N.C. An exemplary Superba heat-setting machine is model number TVP-12-806, which operates with a maximum temperature of 154° C. and typically in the temperature range from 120° C. to 140° C.; and operates with a maximum pressure of 65.26 psi and typical in the pressure range from 22 to 37 psi.
The second type of heat-setting method uses hot atmospheric air. The most common hot atmospheric air heat-setting machine in the background art is referred to as a “Suessen” machine and is made by American Suessen, Inc. of Charlotte, N.C. An exemplary Suessen heat setting machine is the Horauf-Suessen, model number GKK-6R, which typically operates in the temperature range of 160° C. to 210° C.
The crystalline structure of heat-set yarns and the end use performance of the finished carpets produced from heat-set yarns primarily depend on the heat-setting method used in producing the yarn. In general, carpet yarns produced by hot atmospheric air heat-setting machines (e.g., Seussen) have higher bulk and better stain resistance than carpet yarns produced by pressurized steam heat-setting machines (e.g., Superba®).
In addition, there are two types of heat-set carpet yarns: texture set and straight set. Texture set twisted BCF yarns are more versatile in styling than texture set staple yarns. Moreover, it is much cheaper to convert BCF yarns into carpets than it is to convert straight yarns into carpets. The majority of the carpets in today's residential market use texture set yarns.
Texture set yarns are produced by feeding twisted yarn into a stuffer device before directing the stuffed and twisted yarn into a heat-setting machine. FIG. 1 shows a block diagram of a background art apparatus for producing texture set yarns. For heavy denier yarns (e.g., yarns with denier in the range from 2600 to 5000), at least two yarns 1 are fed to the input of a false twisting device 3. For average denier yarns (e.g., yarns with denier in range from 750 to 2600), three or more yarns 1 are fed to the input of a false twisting device 3, as shown in FIG. 1. A twisted yarn 9 emerges from the output of the false twisting device 3 and is fed to the input of a stuffer device 5. The stuffer device 5 crimps (i.e., bends and kinks) the twisted yarn 9. At the output of the stuffer device 5, the stuffed and twisted yarn 12 is piddled into a spaghetti-like pattern and fed onto a flat conveyor belt that carries the stuffed and twisted yarn 12 into a heat-setting machine 7. Heat-setting of the stuffed and twisted yarn 12 is performed in the heat-setting machine 7 by either pressurized steam or hot atmospheric air. The heat-set yarn 14 is then output from the heat-setting machine 7 and wound onto creels by a winder device (not shown).
The apparatus of FIG. 1 is applicable to texture set BCF carpet yarns that are heat-set by pressurized steam heat-setting machines. In addition, the block diagram of FIG. 1, without the stuffer device 3, is also applicable to straight set BCF carpet yarns. However, only texture set staple yarns currently can be produced by hot atmospheric air heat-setting machines. Due to the hairy nature of texture set staple yarns, the twisted yarn ends tend to stay together as a cohesive yarn bundle that can be easily separated and wound onto individual packages at the output of the heat-setting machine. Thus, heat-setting of texture set staple yarns with hot atmospheric air has proven to be an economical and reliable system for producing texture set staple carpet yarns.
However, the apparatus of FIG. 1 cannot be continuously operated for heat-setting texture set BCF yarns with hot atmospheric air. In contrast to the hairy surface characteristics of texture set staple yarns discussed above, texture set BCF yarns have smooth surface characteristics. The smooth surface characteristics of texture set BCF yarns provide no cohesion among the yarn ends of the stuffed and twisted BCF yarn bundle 12. In contrast to the texture set staple yarn bundle discussed above, the yarn ends of the stuffed and twisted BCF yarn bundle 12 tend to lie down separately on the conveyor belt feeding the stuffed and twisted BCF yarn bundle 12 into the heat-setting machine 7 shown in FIG. 1. This lack of cohesion in the stuffed and twisted BCF yarn bundle 12 leads to the problems with continuously processing BCF yarns discussed above. Due to the serious winding problems that occur when using hot atmospheric air in heat-setting of texture set BCF yarns, the apparatus of FIG. 1 is not applicable for heat-setting texture set BCF yarns with hot atmospheric air in a commercial application.
In addition, when hot atmospheric air is used in heat-setting machines, the yarn ends of the stuffed and twisted BCF yarn bundle tend to shrink. Any minor differences in the shrinkage among the yarn ends of the stuffed and twisted BCF yarn bundle can cause serious winding problems due to frequent yarn breaks. Thus, background art hot atmospheric air heat-setting apparatus and methods typically have not been used to continuously process stuffed and twisted BCF yarn in commercial applications.
Despite the problems discussed above, twisted BCF yarn carpets that are heat-set with hot atmospheric air have the significant advantages of providing higher bulk and better stain resistance than carpets that are heat-set with pressurized steam. Therefore, there is a need in the art to increase use of hot atmospheric air heat-setting machines on a commercial scale to heat-set twisted BCF yarns.